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../../principles/referencemodels.rst:165
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An interesting historical discussion of the OSI-TCP/IP debate may be found in [Russel06]_
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../../principles/reliability.rst:206
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A first solution to this problem is to require the physical layer to remain idle for some time after the transmission of each frame. These idle periods can be detected by the receiver and serve as a marker to delineate frame boundaries. Unfortunately, this solution is not acceptable for two reasons. First, some physical layers cannot remain idle and always need to transmit bits. Second, inserting an idle period between frames decreases the maximum bit rate that can be achieved.
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../../principles/sharing.rst:195
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In datagram networks, `Forward Explicit Congestion Notification` (FECN) can be used. One field of the packet header, typically one bit, is used to indicate congestion. When a host sends a packet, the congestion bit is unset. If the packet passes through a congested node, the congestion bit is set. The destination can then determine the current congestion level by measuring the fraction of the packets that it received with the congestion bit set. It may then return this information to the sending host to allow it to adapt its retransmission rate. Compared to packet discarding, the main advantage of FECN is that hosts can detect congestion explicitly without having to rely on packet losses.
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../../principles/transport.rst:109 • ../../principles/transport.rst:122 • ../../principles/transport.rst:213 • ../../principles/transport.rst:526
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The transport layer
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../../bibliography.rst:314
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Russell A., `Rough Consensus and Running Code and the Internet-OSI Standards War <https://dx.doi.org/10.1109/MAHC.2006.42>`_, IEEE Annals of the History of Computing, July-September 2006
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../../glossary.rst:104
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The File Transfer Protocol defined in :rfc:`959` has been the `de facto` protocol to exchange files over the Internet before the widespread adoption of HTTP :rfc:`2616`.
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../../exercises/network.rst:363
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4 via D
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../../exercises/sockets.rst:348
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Here are some exercises that will help you to learn how to use sockets.
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../../principles/reliability.rst:208
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Bit rate and bandwidth
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../../principles/sharing.rst:197
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In virtual circuit networks, packet marking can be improved if the return packets follow the reverse path of the forward packets. It this case, a network node can detect congestion on the forward path (e.g. due to the size of its buffer), but mark the packets on the return path. Marking the return packets (e.g. the acknowledgments used by reliable protocols) provides a faster feedback to the sending hosts compared to FECN. This technique is usually called `Backward Explicit Congestion Notification (BECN)`.
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../../bibliography.rst:317
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Sechrest, S., `An Introductory 4.4BSD Interprocess Communication Tutorial <http://docs.freebsd.org/44doc/psd/20.ipctut/paper.pdf>`_, 4.4BSD Programmer's Supplementary Documentation
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../../glossary.rst:198
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FTP
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../../exercises/network.rst:364
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B
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../../exercises/sockets.rst:364
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Footnotes
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../../principles/network.rst:216
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the `data packets`
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../../principles/reliability.rst:210
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Bit rate and bandwidth are often used to characterize the transmission capacity of the physical service. The original definition of `bandwidth <https://www.merriam-webster.com/dictionary/bandwidth>`_, as listed in the `Webster dictionary <https://www.merriam-webster.com/dictionary>`_ is `a range of radio frequencies which is occupied by a modulated carrier wave, which is assigned to a service, or over which a device can operate`. This definition corresponds to the characteristics of a given transmission medium or receiver. For example, the human ear is able to decode sounds in roughly the 0-20 KHz frequency range. By extension, bandwidth is also used to represent the capacity of a communication system in bits per second. For example, a Gigabit Ethernet link is theoretically capable of transporting one billion bits per second.
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../../principles/transport.rst:115
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The network layer ensures the delivery of packets on a hop-by-hop basis through intermediate nodes. As such, it provides a service to the upper layer. In practice, this layer is usually the `transport layer` that improves the service provided by the `network layer` to make it usable by applications.
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../../bibliography.rst:318
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Scheifler, R., Gettys, J., `X Window System: The Complete Reference to Xlib <http://h30097.www3.hp.com/docs/base_doc/DOCUMENTATION/V51B_ACRO_SUP/XWINSYS.PDF>`_, X Protocol, ICCCM, XLFD, X Version 11, Release 4, Digital Press
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../../glossary.rst:200
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The File Transfer Protocol is defined in :rfc:`959`
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../../exercises/network.rst:364
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1 via B
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